docs: release notes for 0.89

[nishantmonu51]

Release notes for 0.89, covering everything shipped since the 0.88 announcement:

• Highlights: conditional formatting for pivot tables, scheduled canvas PDF reports, dashboard favourites, Spanish localization, invite-time custom attributes, and inline explore dashboards via the explore: block
• Also folds in features that shipped in the 0.88 cycle but were never announced (e.g. model partition skipping, 0.88.x patch fixes)

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!